This invention relates to an upper support in a vehicle suspension assembly and more particularly, to a damping and mounting device, i.e., an upper support for attaching a piston-cylinder type of shock absorber in a suspension system for motor vehicles, to a part of the vehicle body.
In a conventional motor vehicle wheel suspension assembly known as the Macpherson strut type, there are provided a shock absorber comprising a piston and a cylinder, and a coil spring. The shock absorber is secured, at one end of its piston rod, to a part of the vehicle body via a strut mounting functioning as an upper support while on the other hand, the shock absorber is connected, at its cylinder portion, to a wheel axle via a spindle to rotatably support the wheel. The coil spring is so disposed around the shock absorber as to surround adjacent the periphery of the latter, and generally located between an upper spring seat carried by the strut mounting and a lower spring seat carried by the cylinder. The shock absorber and the coil spring cooperate to cushion the body from an oscillating energy received by the said spindle from the road surface, thereby preventing the oscillatory movements from being transferred to the body.
The strut mounting comprises: a cylindrical inner member to which the piston rod of the shock absorber is connected; a generally cylindrical outer member at which the strut mounting is fixed to the vehicle body; and an annular resilient member (usually made of rubber) disposed between the inner and outer members, and vulcanized thereto or held therein by other means. The resilient member absorbs a residual oscillatory movement of the vehicle wheel which has not been absorbed by the said shock absorber and coil spring, thereby preventing the transfer of such movement to the vehicle body.
While the resilient member is subjected to a shear stress when the oscillatory movements are transferred from the piston rod in the axial direction thereof, it is required, for maintaining a driving comfort of the vehicle under such condition, that the resilient member have non-linear spring characteristics, i.e., it be provided with the structure allowing it to exhibit soft spring characteristics during application of low loads, and at the same time hard spring characteristics which means that the resilient member will not be deformed to a large extent upon application of high loads. To meet the above requirement, it has been proposed to provide an upper support with a suitable stopper means which prevents the resilient member from being deformed beyond a certain limit upon application of a high load thereto. The proposed upper support with such conventional structure, however, has a problem that they are likely to generate unusual sounds or noises due to severe collision of the resilient member with the stopper means upon transfer of a high oscillatory load to the resilient member. Such noises can be readily heard by the vehicle passengers and be a source of discomfort to them, especially where the upper support of that kind is used in a rear wheel suspension which is usually located near a vehicle compartment. The present invention was made in view of the above situation.